Process of making pressure sensitive record material



TENT OFFICE PROCESS OF MAKING ,PRES SURE SENSITIVE; RECORD MATERIAL Barrett K. Green, Dayton, Ohio, assig nor to The National Cash Register Company,

Dayton,

Ohio, a corporationiof Maryland 2 Claims.

This invention relates. to improvements in process of making a pressure-sensitive record material. This application is a division of the pending applicationcf Barrett K. Green, Serial No. 784,939, filed November 8, 1947, for Process of making pressure-sensitive record material.

The principal object of this invention is to provide a process of making a pressure-sensitive record material, on which a mark of distinctive color may be produced by the mere application of, localized presser, and which is not subject to the disadvantages'inherent in the pressure-sensitive record material disclosed in United States Letters Patent No. 2,299,693, patented October 20, 1942, on theapplication filed by Barrett K. Green on February'- 23, 1940. That patent discloses a: pressure-sensitive record material including the combinationoi an insulating medium, a rupturable solid material such as gum dammar, having inciudedtherein interspersed droplets of a plurality of liquid reagents, which are chemicallyreactive to produce a distinctive color in the rec-. ord material at the points of application oflocalized pressure thereto, such pressure rupturing the insulating medium to permit chemical reac tion between the two liquid reagents. The two reagents disclosed'in' this patent are gallic acid and ferric ammonium sulphate, each dissolveda These reagents are ionized by the" glycerine, which constitutes anpionizing medium, is

in glycerine;

and the chemical reaction proceeds by interchange of ions when the two solutions are allowed to mix, upon the rupture of the insulating medium. The reaction disclosed in that patent depends upon the presence of the reagents inan ionizing medium. However, any available ioniz: ing medium is hygroscopic, with the result thatv the record material, made in accordance with.

this patent, is sensitive to an excess of moisture, and conditions of high humidity'may cause the insulating mediumto cease to be eiiective, with the result.thatthechemical reaction takes place without any application of localized press.ure,.

and the record material is stained and discolcred, so that it ceasesto be useful.

As stated above,- the. principal object of the;

Another object of the present invention is to:

provide a process of making a record material upon which a mark of distinctive color may be ill.)

ized pressure thereto, by such mere application of localized" pressure, .and which will not become discolored or stained due to the effect of light, atmospheric conditions, or aging.

In short, it is the object of this invention toprovide a process of making pressure-sensitive record material iirwhich the mark of distinctive color will be produced only at the points of application of localized pressure, and at. no other points, and under no other conditions.

Another object of'thisinvention is to provide a process of making a pressure-sensitive record material in which the mark of distinctive color isaproduced by the chemical reaction of colorforming reactants, inthe absence of any liquid ionizing medium therefor.

A further object of this invention is to provide a process of making a pressure-sensitive record material in whicha mark of distinctive color is produced by a reaction between solid particles of color-forming reactants.

Further objects, and objects relating to details and economies of operation, will definitely appear from the detailed-description to follow. The objects of this invention have been attained by the several embodimentsthereof described in detail in the following specification. This invention is clearly defined and pointed out in the appended claims.

In general, the presentinvention contemplates a process of making a pressure-sensitive record material including the forming of a film-like deposit of solid particles of a plurality of colorforrning reactants disposed in contiguity with each other, such reactants being so selected that they react, in the absence of a liquid ionizing medium for the reactants, to form a distinctive color when brought into adsorption contact with each other, and a solid insulating medium insulating said reactants from color-forming reaction contact: with each. other. Upon application of-- localized pressureto the record. material, as-

by-drawing a stylus acrossit, the insulating me-.

dium' is ruptured at thepoints of' application of i said localized pressure, andsuch rupture permits color-forming reaction contact between the reactants. at such points, in the absence of any liquid ionizingmedium for said reactants. The

result is that a mark of distinctive color is produced by the mere application of localized pressure.

The; color reaction employed is of the, socalled, adsorption. type wherein an inorganic compound causes a color change in an organic produced, atlthepoints of applicationof localcompound comin in 0- 00ntact therewith.

Of the reactant materials employed the organic material is an electron donor aromatic compound having a double bond system which is convertible to a more highly polarized conjugated form upon taking part in an electron acceptor-donor solid surface chemical reaction, giving it a distinctive color, and the inorganic material is a material which is an acid relative to the organic material so as to be an electron acceptor when in adsorption contact therewith. Both materials are in fine particle form in order to furnish a large reactant surface area per unit area of the record material which enhances the depth of color per unit area of the record material.

According to one embodiment of the invention, solid particles of one of the color-forming reactants are carried by and dispersed in a solid insulating medium, to which a coating of solid particles of another color-forming reactant is applied. In this case, the application of localized pressure ruptures the solid insulating medium, at the points of application of such pressure, and brings about color-forming reaction contact between the solid particles of color-forming reactants at such points, thus producing the mark of distinctive color. Preferably, this pressuresensitive record material includes as a supporting member a base web, such as a fibrous web of paper or the like, to which the coating of solid insulating medium and the color-forming reactants is applied.

The insulating medium is a pressure-rupture.- ble film derived from an organic film-forming hydrophilic colloid substance.

Since it is diificult to show precisely the spatial relationship between the solid particles of colorforming reactants, the solid insulating medium, and the base web, it is preferred not to attempt to illustrate any embodiment of this invention by drawings.

In the following examples, there will be described embodiments of this invention, by means of which the objects of the invention have been successfully attained.

The preferred embodiment of this invention produces a pressure-sensitive record material consisting of a web of paper having applied thereto a coating comprising casein as the solid insulating medium and two color-forming reactants; namely, kaolin and the compound bis(p-dimethylaminophenyl) methanol, also known as Michlers hydrol and having the structure In this record material, the casein forms the solid insulating medium, insulating the solid particles of kaolin and Michlers hydrol from colorforming reaction contact with each other, until the application of localized pressure ruptures the insulating medium at the points 'of application of such pressure, permitting color-forming reaction contact between the particles, producing a dark blue mark; The record material is normally white or light gray in color.

According to this embodiment of the invention, this record material has been made successfully by coating a base web of paper with a solution of casein having solid particles of kaolin dispersed therein, the. ratio of kaolin to casein being about ten to one. The paper so coated was dried and suitably calendered, and then the coated side of the paper was treated with a 3% by weight solution of Michlers hydrol dissolved in ethyl alcohol saturated with potassium carbonate. The excess of this solution was removed, and the treated paper was dried, evaporating the solvent, and was then ready for use.

Another embodiment of this invention produces a record material consisting of a web of paper having applied thereto a coating comprising casein as thesolid insulating medium and two color-forming reactants; namely, kaolin and. the compound bis(p-dimethylaminophenyl)- methoxy-methane, also known as methyl ether of Michlers hydrol, having the structural formula 7 (CH3) 2N- N(CHa)a \g/ V l O-CHa According to this embodiment, the casein constitutes the solid medium insulating the solid particles of kaolin and of methyl ether of Michlers hydrol from color-forming reaction contact with each other, and, when this solid insulating medium is ruptured by the application of localized pressure, color-forming reaction contact be tween the particles is permitted at the points of application of such pressure, producing a dark blue mark upon thenormally white or grayish record material at such points.

In this embodiment of the invention, record material has been successfully made by coating paper with a casein solution having dispersed therein solid particles of kaolin, the ratio by weight of kaolin to casein being about ten to one. The coating thus applied having been dried, the coated side of the paper was then treated with a 3% by weight solution of methyl ether of Michlers hydrol in ethyl alcohol saturated with potassium carbonate. The excess of this solution was removed, and the treated paper was dried to remove the solvent.

When the ingredients of either embodiment are applied to the paper as a coating thereon, such coating should weigh about .0023 per square foot of surface and have a thickness of the order from .0005 to .001 inch. The thickness of the coating varies, of course, with the treatment to which the record material is subjected in finishing. The solid particles of kaolin in this record material may be of about the order of ten microns in diameter, although considerable variation in particle size is possible without any ill effects. Particle size of the Michlers hydrol or the methyl ether of Michlers hydrol is largely determined by the method of application of those ingredients. The particles of these reactants may be as large as ten microns in diameter and frequently are much smaller.

Other organic film-forming hydrophilic colloid substances such as gelatin, methyl cellulose, starch, polyvinyl alcohol, and animal glue are representative materials that may be substituted for casein as the solid insulating medium. Any of the following inorganic materials may be su stituted for kaolin as one of the color-forming reactants: attapulgite (Attapulgus clay), D310-' accuse When any of these materials are substituted for the kaolin in this combination, the resulting record material will be white or bluish white in color, and a dark blue mark will appear thereon as the result of the application of localized pressure.

A method constituting one embodiment of this invention that has been used successfully to make the pressure-sensitive record material described above is as follows: A slurry of kaolin and water was prepared including fifty parts by weight of kaolin to fifty parts by weight of water, and a small amount of a suitable dispersing agent, such as sodium metaphosphate, for instance, in the proper ion of 0.075% by weight was added to facilitate he dispersion of the particles of kaolin throughout the slurry. The addition of this dispersing agent reduces the viscosity of the slurry considerably, thus facilitating its mixing and application, and also preventing the settling of the solid particles of kaolin. A 20% by weight solution of casein in water was formed by, first, dispersing the casein in cold water by stirring for fifteen minutes at room temperature and, then, heating up to 60 degrees centigrade. Five parts by weight of a 28% ammonium hydroxide solution-that is, one having a specific gravity of 25.9 Be, at

were then added to the hot casein solution, which was stirred for about fifteen minutes and allowed to cool to room temperature. The kaolin slurry the alkaline casein solution were then thoroughly and blended, in the ratio of ten parts by weight of kaolin to one part of and, at this stage, a small percentagefor instance, about 0.05% by weight-of a solution of equal parts by weight of tributyl phos phate in alcohol, or other antifoaming agent, was added. This mixture of the kaolin slurry and the casein solution was then applied as a coating to the paper, and the coated paper was dried and calendered or treated in any desired way to give the proper surface finish. A solution in toluene of about 3% by weight of either Michlers hydrol or the methyl ether of Michlers hydrol" was then applied to the coated side of the paper,

the excess of this solution was removed in any suitable way, as by passing under a doctor blade, and then the treated paper was dried to evaporate the toluene, and was ready for use.

The pressure-sensitive record materials disclosed herein are not claimed in this application but are disclosed and claimed in the ponding application of Barrett K. Green, Serial No. 784,938, filed November 8, 1947, for Pressuresensitive record material, and in a division thereof, Serial No. 59,425, filed November 10, 1948.

It is understood that the process of making a pressure sensitive record material described erein is susceptible of considerable variation without departing from the spirit of the invention.

What is claimed is:

.l. The process of making a pressure-sensitive record material including the forming on a supporting member a film-like deposit of solid particles of aplurality of adsorption color-forming reactants disposed in contiguity with other and a solid insulating medium, derived from an organic film-forming hydrophilic colloid substance, insulating said reactant particles from color-forming reaction with each other, at least one of said reactants being an inorganic compound and at least another one of said reactants being an organic compound adsorbabl therewith, and said reactants being so selected as to react, in the absence of a liquid ionizing medium for the reactants, to form a distinctive color when brought into adsorption contact with each other, one of said color-forming reactants being a compound having the structure cnomono:

wherein R is selected from the group consisting of OH and OCHs and the inorganic reactant being in fine particle form providing a large adsorbent surface area and which an acid relative to the organic reactant so as to be an electron acceptor when in adsorption contact with said organic reactant.

2. The process of making a pressure-sensitive record material including the steps of coating a supporting member with a film of solid insulating material, derived from an organic film-forming hydrophilic colloid substance, having particles of a first color-forming solid reactant dispersed therein, and depositing on said film particles of a second color-forming solid reactant, one or" said reactants being an inorganic compound and the other of said reactants being an organic compound adsorbable therewith, and said reactants being so selected as to form a distinctive color when brought into adsorption contact with each other, and said solid insulating material being such as to insulate the reactants from color-forming reaction contact with each other, the second color-forming reactant being a compound of the structure wherein R is selected from the group consisting of OH and OCH; and the inorganic reactant being in fine particle form providing a large adsorbent surface area and which is an acid relative to the organic reactant so as to be an electron acceptor when in adsorption contact with said organic reactant.

BARRETT K. GREEN.

REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Number Country Date 550,332 Great Britain Jan. 4, 1943 Certificate of Correction. Patent No. 2,505,484 April 25, 1950 BARRETT K. GREEN It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 11, for the Word presser read pressure; column 4, line 49, after .0023 insert pound;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office;

Signed and sealed this 8th day of August, A. D. 1950.;

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

1. THE PROCESS OF MAKING A PRESSURE-SENSITIVE RECORD MATERIAL INCLUDING THE FORMING ON A SUPPORTING MEMBER A FILM-LIKE DEPOSIT OF SOLID PARTICLES OF A PLURALITY OF ADSORPTION COLOR-FORMING REACTANTS DISPOSED IN CONTIGUITY WITH EACH OTHER AND A SOLID INSULATING MEDIUM, DERIVED FROM AN ORGANIC FILM-FORMING HYDROPHLIC COLLOID SUBSTANCE, INSULATING SAID REACTANT PARTICLES FROM COLOR-FORMING REACTION WITH EACH OTHER, AT LEAST ONE OF SAID RECTANTS BEING AN INORGANIC COMPOUND AND AT LEAST ANOTHER ONE OF SAID REACTANTS BEING AN ORGANIC COMPOUND ADSORBABLE THEREWITH, AND SAID REACTANTS BEING SO SELECTED AS TO REACT, IN THE ABSENCE OF LIQUID IONIZING MEDIUM FOR THE REACTANTS, TO FORM A DISTINCTIVE COLOR WHEN BROUGHT INTO ADSORPTION CONTACT WITH EACH OTHER, ONE OF SAID COLOR-FORMING REACTANTS BEING A COMPOUND HAVING THE STRUCTURE 